Zero-Point Bubbles in Liquids

Briscoe, C. V.; Choi, Sang‐Il; Stewart, Andrew

doi:10.1103/physrevlett.20.493

Cited by 91 publications

(21 citation statements)

References 12 publications

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“…Figure 1 also shows the curve corresponding to Eq. (1) that is based on the assumption of the infinite spherical potential well [4]. One can see that this curve agrees in the slope with those calculated for finite potential wells in the case of larger sizes.…”

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confidence: 75%

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Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers

Palacio

Djourelov

Kuriplach

et al. 2007

Phys. Status Solidi (c)

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PACS 71.60.+z, 78.70.Bj Doppler broadening of annihilation radiation (DBAR) measurements have been performed in uniaxially hot-drawn poly(methylmethacrylate) (PMMA) samples. The DBAR spectra were deconvoluted into three Gaussians. The full width at half-maximum of the narrow component which is due to para-Positronium (pPs) self-annihilation is under discussion. An anisotropy of the free volume holes (FVHs) has been detected by measuring the deformed samples at the stretching and transverse directions. The sample deformed at 280% was also measured as a function of the orientation angle (0 • -90 • ) with respect to the stretching direction. The momentum distribution of p-Ps, which is considered as a structureless particle confined in FVH of ellipsoidal or cuboid shape, was calculated as a function of the potential well size and depth and compared with experiment.1 Introduction Positron annihilation lifetime spectroscopy (PALS) has been proven to be a very sensitive technique to study free-volume holes (FVHs) in polymers [1,2]. When a positron (e + ) enters condensed matter, after thermalization and diffusion, it eventually annihilates with an electron (e − ) of the medium, mostly by two 511 keV gamma quanta. Before the annihilation, the e + exists as a "free" positron (it annihilates directly with an e − with a lifetime (τ ) of ∼ 0.3-0.5 ns), or forms a positronium (Ps). In condensed matter, the ortho-positronium (o-Ps) lifetime (τ o−P s ), which is 142 ns in vacuum, is quenched to some nanoseconds as e + of the o-Ps atom annihilates with e − from the surrounding molecules (the socalled pick-off process). There is a well-known correlation between the radius (R) of spherical FVH and τ o−P s derived from the Tao-Eldrup model [3].The second most frequently used technique to detect open volume defects and to study their properties is the Doppler broadening of annihilation radiation (DBAR). In DBAR the interest is focussed on the 511 keV line, which is Doppler-broadened due to the momentum component P z of the e + − e − pair, where z is the detection direction. The peak is a superposition of a narrow (approximately a Gaussian) component due to the self-annihilation of para-positronium (p-Ps) and broader Gaussian-like distributions due to free e + and o-Ps pick-off annihilation [2,3]. The narrow component reflects the localization momentum of the p-Ps inside FVH and according to the Heisenberg uncertainty principle, it is sensitive to the FVH size.In a simple quantum-mechanical model, it is assumed that the Ps is confined in a spherically shaped potential well of infinite depth and radius R with a spatial overlap of the Ps wave function with molecules within a layer δR of the potential wall. The relationship between θ 1

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supporting

confidence: 75%

“…The relationship between θ 1 2 (the full width at half-maximum (FWHM) of the narrow Gaussian) and the radius (R) inÅ of FVH in a given momentum direction is empirically found [3,4]:…”

mentioning

confidence: 99%

Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers

Palacio

Djourelov

Kuriplach

et al. 2007

Phys. Status Solidi (c)

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“…comparison with equation (37) indicates that, (to first order), an electric dipole moment, µ elec , can be associated with each k-state such that [175],…”

Section: Ps In Electric and Magnetic Fieldsmentioning

confidence: 99%

“…The work of Deutsch and colleagues did not immediately provoke widespread experimental Ps research, although in the following decades some measurements were conducted, including studies of magnetic quenching [29][30][31] and electric field effects on Ps in gases [32], (unsuccessful) searches for Ps Lyman alpha lines [33], measurements of Ps formation [34] and diffusion [35] in solid materials, powders [36], and liquids [37], positron polarization measurements [38], symmetry tests [39] and more refined hyperfine interval measurements [40], as well as Ps decay rate measurements [41]. All of this work utilized positrons emitted from radioactive sources and captured in the material in which Ps formation occurred.…”

Section: Introductionmentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

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Abstract. The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥10 6 ) accumulated in such a device may be ejected all at once, so as to generate an intense pulse. Standard bunching techniques can produce pulses with ns (mm) temporal (spatial) beam profiles. These pulses can be converted into a dilute Ps gas in vacuum with densities on the order of 10 7 cm −3 which can be probed by standard ns pulsed laser systems. This allows for the efficient production of excited Ps states, including long-lived Rydberg states, which in turn facilitates numerous experimental programs, such as precision optical and microwave spectroscopy of Ps, the application of Stark deceleration methods to guide, decelerate and focus Rydberg Ps beams, and studies of the interactions of such beams with other atomic and molecular species. These methods are also applicable to antihydrogen production and spectroscopic studies of energy levels and resonances in positronium ions and molecules. A summary of recent progress in this area will be given, with the objective of providing an overview of the field as it currently exists, and a brief discussion of some future directions.

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“…In the second case the used formulas were taken from the papers by Eldrup et al [12] and Briscoe et al [13]:…”

Section: Experimental and Resultsmentioning

confidence: 99%

Positron Annihilation in Obsidians

Chojcan

Sachanbiński

1995

Acta Phys. Pol. A

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Positron lifetime spectra as well as one-dimensional angular correlations of positron annihilation radiation were measured at room temperature for samples of rhyolitic obsidian coming from Iceland, Italy and Armenia. The samples were of different age. One specimen (originating from Iceland) . was relatively young, formed in 1980. The others were much older, collected during the 19th century. It was found that the linear dimensions of pores trapping the positronium atoms before their decay as well as the pore concentration in all old obsidians are almost the same independently of the place of their formation. Simultaneously the concentration of the pores in the young sample is about five times lower than in the old specimens. Basing on the result it is suggested to extend the study in order to find out if positron annihilation can be used for the investigation of the age of the volcanic accumulations containing obsidian.

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Zero-Point Bubbles in Liquids

Cited by 91 publications

References 12 publications

Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers

Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers

Experimental progress in positronium laser physics

Positron Annihilation in Obsidians

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